Seeing mucus or “snot” emerge from the corner of your eye when blowing your nose can be startling. This unusual event is not a sign of a severe problem, but a direct demonstration of the intricate plumbing system connecting your eyes and nasal cavity. This anatomical pathway, which normally manages tear drainage, can be temporarily overwhelmed by pressure changes in the nose. Understanding this connection explains why blowing your nose can produce such a surprising result.
The Plumbing: Connecting the Nose and Eye
The primary connection between the eye and the nose is the nasolacrimal system, often called the tear drainage system. This system is designed to be a one-way street, transporting tears from the eye’s surface down into the nasal cavity. Tears are first collected through tiny openings called puncta, located in the inner corner of the upper and lower eyelids near the nose.
From the puncta, tears travel through small canals called canaliculi into the lacrimal sac, which acts as a temporary reservoir. The lacrimal sac then narrows into the nasolacrimal duct, a passageway that descends through the nasal bone. This duct empties directly into the lower part of the nasal cavity, or inferior nasal meatus. This connection explains why crying or applying eye drops can cause the nose to run or allow a person to taste medication.
The drainage system includes several mucosal folds and valves, such as the Valve of Hasner at the duct’s lower end. These are designed to prevent material from flowing backward into the eye. However, this delicate one-way mechanism is vulnerable to high pressure exerted from the nasal side. The system’s typical function is to drain tears into the nose.
Why Blowing Your Nose Causes Reverse Flow
The symptom occurs because forceful nose blowing significantly increases the air pressure within the nasal cavity and sinuses. When both nostrils are compressed during a vigorous blow, this pressure has nowhere to go but up, forcing air and mucus backward through any available opening. The nasolacrimal duct, despite its protective valves, becomes a reverse conduit under this high pressure.
The pressure generated is strong enough to overcome the resistance of the Hasner valve. This pushes the contents of the nasal cavity—including mucus—up through the duct and lacrimal sac. The material then exits the system through the puncta in the inner corner of the eye. Reverse flow is particularly likely when a person is congested from a cold or allergies.
Congestion exacerbates the issue by causing the nasal lining to swell, creating partial blockages that further increase internal pressure during blowing. People with naturally wider tear ducts or minor anatomical variations may be more susceptible to this reverse flow. This movement of mucus is a transient mechanical failure of the one-way drainage system due to an extreme pressure gradient.
When This Symptom Warrants a Doctor Visit
While the occasional appearance of mucus from the eye is primarily a mechanical quirk, certain accompanying symptoms suggest a need for medical evaluation. A consultation is appropriate if the reverse flow is chronic, happens even when a person is not congested, or is accompanied by persistent pain or swelling around the eye. Discharge that is bloody or colored mucus lasting longer than a week may indicate a bacterial infection requiring treatment.
Immediate medical attention is necessary if the eye area shows worsening pain, swelling, or redness, or if a person experiences double vision, vision changes, or a high fever. These symptoms could signal a more serious complication, such as the spread of a sinus infection to the eye socket. To mitigate the risk of reverse flow, individuals should adopt a gentler nose-blowing technique, focusing on exhaling softly through one nostril at a time. An ophthalmologist or an Ear, Nose, and Throat (ENT) specialist can assess the tear drainage system if the symptom persists.